Aluminum sticking damages casting surface quality and shortens mold service‑life. Melt scouring, nitriding‑layer failure, surface decarburization, release‑agent spraying and local over‑heating jointly induce sticking for LPDC, gravity and CPC counter‑pressure casting production.
Metallurgical sticking mechanism: high‑temperature molten aluminum wets exposed steel substrate, forms Fe‑Al intermetallic compound layer. Once nitriding protective layer is worn or broken, aluminum alloy directly contacts H13 matrix and generates sticking build‑up for EV structural‑part mold.
High‑melt‑scour zone accelerates nitriding‑layer consumption. Gating in‑gate position suffers continuous high‑velocity aluminum flow erosion; nitriding layer gradually thins, and sticking defect first appears at runner‑cavity junction for CPC counter‑pressure casting mold.
Decarburized surface layer from improper mold heat‑treatment is high‑risk sticking source. Decarburized zone has reduced surface hardness; even intact nitriding treatment cannot fully compensate substrate surface performance deficit for gravity casting mold mass‑production.
Release‑agent spraying defect triggers local sticking: insufficient coating thickness, spray shadow at deep‑recess geometry, over‑high spray‑air pressure blowing away protective film. 37 % on‑site sticking incidents relate to release‑agent application abnormality for LPDC casting mold aluminum wheel production.
Local mold over‑temperature amplifies wetting tendency. Cavity surface temperature exceeding 560 ℃ greatly improves aluminum wettability toward steel surface; insufficient cooling at hot‑spot area speeds up sticking accumulation for aluminum casting mold.
Polishing operation risk: over‑aggressive polishing removes partial nitriding‑protection layer. Cavity corner and flow‑impact position shall adopt controlled‑polishing to avoid thinning nitriding layer below 0.06 mm for EV structural‑part batches.
Sticking early warning signal: periodic surface burr on casting fixed‑position, increased mold‑opening resistance. If ignored, intermetallic layer thickens; hard sticking lump causes casting tearing and cavity surface plastic damage for CPC counter‑pressure casting mold.
On‑site cleaning pitfall: force‑grinding sticking lump without controlled removal. Improper manual grinding creates micro‑notches on cavity surface; these notches become new sticking initiation points for gravity casting mold maintenance.
Repair workflow for sticking‑damaged cavity: fully remove Fe‑Al compound layer, inspect substrate for decarburization, perform local re‑nitriding. Partial nitriding repair avoids over‑brittleness of unaffected cavity area for LPDC casting mold.
Design preventive measure: strengthen cooling layout at in‑gate and high‑scour region. Reduce peak cavity surface temperature below 520 ℃; adopt blended smooth transition to minimise local melt impact velocity for aluminum casting mold.
Cross‑border communication note: simply increasing release‑agent concentration cannot resolve substrate‑origin sticking. Many overseas foundries over‑apply release‑agent, introducing carbon‑related porosity while sticking defect remains unsolved.
FAQ
Q: What intermetallic compound forms when molten aluminum sticks onto exposed H13 steel substrate?
A: Fe‑Al intermetallic compound layer forms via metallurgical wetting reaction.
Q: Where does aluminum sticking defect most frequently first emerge inside mold cavity?
A: In‑gate and runner‑cavity junction subjected to high‑velocity melt scouring.
Q: What cavity surface temperature threshold greatly elevates aluminum wetting‑sticking risk?
A: Cavity surface temperature above 560 ℃ significantly increases sticking tendency.
Q: What percentage of field sticking incidents correlate with release‑agent spraying abnormality?
A: 37 % sticking problems originate from improper release‑agent spraying execution.
Q: What hidden risk comes from excessive polishing on nitrided mold cavity surface?
A: Excessive polishing thins nitriding protective layer below effective thickness threshold.
Q: What negative consequence arises from brute‑force grinding of sticking lump on cavity?
A: Manual grinding generates micro‑notches acting as new sticking initiation sites.
Q: Why cannot higher release‑agent concentration fix substrate‑caused aluminum sticking?
A: Sticking originates from damaged substrate/nitriding layer; excess agent brings carbon‑porosity risk.
